The present invention relates to a wafer transport apparatus for use in an ion implantation apparatus which performs ion implantation processing of wafers of material utilized to manufacture semiconductor devices, e.g. wafers of crystalline silicon (referred to in the following specification and claims simply as "wafers"). As is well known an ion implantation apparatus includes means for transporting wafers from the external atmosphere into an auxiliary vacuum chamber, and from there into a vacuum processing chamber in which ion implantation is performed. The wafers are then transferred from the vacuum processing chamber back to the auxiliary vacuum chamber and from there back out into the atmosphere. With prior art types of wafer transport apparatus for such an application, the weight of each wafer is employed to provide the motive force for this transportation, i.e. the force of gravity acting on each wafer is employed to slide the wafer along downwardly sloping surfaces. More specifically, such a prior art wafer transport apparatus comprises first inclined surface guidance means for transporting wafers from the external atmosphere into an auxiliary vacuum chamber, and from there into a vacuum processing chamber, together with second inclined surface guidance means, separate from the first surface guidance means, for transferring the wafers from the vacuum processing chamber, through an auxiliary vacuum chamber, back to the external atmosphere. The wafers are successively moved downward as they slide along the inclined guidance surfaces, to be thereby successively transported to requisite positions.
Such a prior art wafer transport apparatus has the advantage that no drive apparatus is required. However it presents the following problems. Firstly, if a layer of photo-resist has been formed on each wafer, then sticking of the wafers may occur during the gravity transportation process, causing interruptions in production. Furthermore, the wafers may adhere to stopper members which are provided in the inclined surface guidance means. This problem can occur even with wafers which do not have a layer of photo-resist formed thereon. In addition, impact of the wafers against the stopper members results in the formation and accumulation of small wafer particles, resulting in build-up of dust, and also causes damage to the wafers.
Furthermore with such a prior art wafer transport apparatus, problems arise with regard to sequential transfer of wafers from a wafer cassette to an ion implantation processing section, and subsequent transfer of wafers from the ion implantation processing section to be loaded into a wafer cassette. Due to the above reasons, prior art types of wafer transport apparatus present serious problems with regard to production efficiency.